This little form will let you upload a JPEG, and a PNG with a mask in the
alpha channel. It will then combine these and return the resulting JPEG
to you for your "JPEG with alpha" pleasure.

JPEG Image: PNG Mask:

Note: It won't be masked when it returns, you have to use it with the magic
Javascript for that. This is just a bare image coming back.

Also note: This web server is running Lighttpd and will fail if you use curl
to drive it unless you supress the "Expect:" header with a -H "Expect: ".

As long as we are noting: I might retain a copy of your image for debugging and
tuning, and this is just a tiny slice of a VPS, please don't kill it. The source
is available at http://jim.studt.net/jpeg-alpha/ if you need to do a large number
of files.